A computer system may be coupled to a camera system, which is configured to acquire video of a user. Through analysis of the video, the user's posture and/or gestures may be recognized and provided as input to software executing on the computer system. Input provided in this manner is especially attractive in video-game applications. In particular, the computer system may be configured to observe and decipher real-world postures and/or gestures corresponding to in-game actions. The task of determining a user's posture and/or gesture is not trivial, however; it requires a sophisticated combination of hardware and software. One of the outstanding challenges in this area is to accurately distinguish the user's body from a complex background in the acquired depth video.